Subject: [XCON] Conference Controllers and Mixers

From: roni.even at polycom.co.il (Even, Roni)
Date: Thu Jul 17 02:10:47 2003

Hi,
I think that I would like to clarify the conferencing architecture. If you
will look at the sipping conference framework draft that was written by
Jonathan Rosenberg you will see three different logical entities. The
conference policy server, the focus and the mixers. You can also look at it
as an application server that includes the conference policy, a focus which
does call signaling with EPs or other focus and a mixer that mixes the media
according to the information from the focus. 
The XCON is addressing the issue of how an application from a user can
manipulate the conference policy (including media policy). It is not
addressing the decomposition of the conference server. For example you can
say that a conferencing bridge can be one physical unit that includes both
the focus and the mixer. You can have them in a physical decomposition (BTW
there is work done by the ITU on H.248.19 which is a package for this
decomposition). Now in you example the distributed conference can be done
either by having one focus (or MC (MGC) in Megaco terms) and many mixers (or
MPs in Megaco terms) in that case it is one conference that has one focus.
Another way is to have one application server that will  handle many
conferencing server (MCUs) composed out of focus and mixers, this is a
cascaded conference. The cascaded solution involves less communication
between the entities and is more suitable, in my opinion, to geographically
distributed architecture. It is true that we do not address the issue of the
communication between the focus and the conference policy server (or
application server) but rather about how user application can define the
policy. I assume that this connection can be based on SIP (look at 3GPP AS
to MRF interface as an example)
Regards

Roni Even

**********************************
Roni Even
VP Product Planning
Polycom Network Systems

Tel: +972-3-9251200
Mobile: +972-55-481099
email: [email-masked]
*************************************

-----Original Message-----
From: Bob Hughes [mailto:[email-masked]]
Sent: Wednesday, July 16, 2003 6:18 PM
To: [email-masked]
Subject: [XCON] Conference Controllers and Mixers

Steve Fisher wrote the following in a note with a different subject header
and I wanted to add a couple of comments in favor of moving the
mixer/controller protocol back in scope.

Rohan,

In your response to Eric you state the following goal for xcon:

"The goal is to allow customers to select a
conferencing application that can work with many vendor's mixers and
conference servers."

I'm puzzled how this goal can be achieved when the protocol between the
application server and the mixers is explicitly out of scope for xcon?
According to the charter, the following is out of scope: "Protocol used
between the conference controller and the mixer(s)."

Steve

Please consider:  if conference participants were in different geographies
(Europe and Aisia, for example) and an enterprise wished to mix in each
geography to minimize traffic between geos, it is unrealistic to think that
the mixer in each geography will always be from the same supplier.  It
seems that a single focus, in this case, is in control of a call with
multiple mixers (probably from different vendors) and the question of
protocol becomes pretty important.

Please consider also:  If the UA has conferencing capability (for, say,
between 3-6 participants) and the user still accesses the conference server
(something that certainly happens in real life as not many people can
handle or be bothered with the key strokes needed to set up conferences on
a phone), shouldn't the focus have the ability to establish the conference
on the UA itself (for small conferences and assuming the conference server
has some awareness of the UA's mixing capability)?  A definition of the
controller/mixer protocol would be useful here, too.  This is a huge thing
for the enterprise as many conferences are small and the investment in UAs
is large.  It seems very desirable if UA based conferencing can be
accomplished in manner indistinguishable from central mixing from the end
user's perspective.

Thanks.

Program Manager, VoIP and Voice/Data Convergence
eBusiness On Demand Transformation;  IT Enablement
914-514-5016:  TL 725-7242

_______________________________________________
XCON mailing list
[email-masked]
http://www.softarmor.com/mailman/listinfo/xcon